"It's curious because certain things will be a bit edgier and more challenging than they were, then again in the early films the girls are puffing away on cigarettes and of course you can't do that now," says Parker.

Colin Firth (left) and Rupert Everett do battle with the naughty girls

"I hope we have come up with something that's fresh and stands on its own."

The idea of a new version of an old favourite was suggested by Everett, who worked with Parker on An Ideal Husband and The Importance of Being Earnest.

Everett takes the dual role of the school headmistress and her brother, memorably played by Alastair Sim in two of the original movies.

"You should never really try and take on a role that has been played to the hilt - there is very little chance that you can do better," he admits.

Firth suggests: "You're very attractive - you're much more attractive than he ever was."

Lily Cole (left) and Mischa Barton were at a Cannes St Trinian's party

Among the figures used as inspiration for the headmistress is Camilla Parker Bowles, Everett confesses.

"She's a marvellous woman," he says. "She's got a sense of humour, and she likes a drink and a cigarette - she's my kind of girl."

Firth, who also starred in The Importance of Being Earnest, plays an MP planning to turn the school into a respectable institution when it nears bankruptcy.

His battle with the schoolgirls over the fate of St Trinian's sees him "humiliated in as many ways as possible", according to Parker.

"I am begging them to kill me off in this one," says Firth, in response to a question about possible sequels to the film.

St Trinian's has been filming in Trafalgar Square, London

"Let's see how people like this one first," says Parker.

He is co-directing the film with Barnaby Thompson, previously producer on a number of Parker's films.

The cast also includes Mischa Barton, star of US TV series The OC, Casino Royale actress Caterina Murino and TV presenter and comedian Russell Brand.

St Trinian's is due to finish shooting next week, having been filmed in and around Ealing Studios in west London.

Ealing Studios is famed for producing some of Britain's best-loved comedies in the 1940s and 50s, including Whisky Galore and The Ladykillers.

It returned to film-making in 2002 and has made one or two films a year since, but is now aiming to increase that to between three and six a year.

"We will be operating very much as a boutique version of the American studios," says managing director James Spring.

"In the same way that taking on Ealing Studios we have a great responsibility to its history, with St Trinian's we have a great responsibility to that history.

"They are great fun comedies, but with a real anarchic flavour to them.

"The film that we are making is very much based upon the values of the old St Trinian's movies."